Extendible and retractable cover apparatus for swimming pools



Aug. 28, 1962 J. H. LAMB 3,050,743

EXTENDIBLE AND RETRACTABLE COVER APPARATUS FOR SWIMMING POOLS Filed Aug. 7, 1961 4 Sheets-Sheet 1 Q "'m N Ala I o 0 0] o I 11) h- 0 Q INVENTOR. JOE H. LAMB MM;

ATTORNEYS Aug. 28, 1962 EXTENDIBLE AND RETRACTABLE COVER APPARATUS FOR SWIMMING POOLS Filed Aug. 7, 1961 J. H. LAMB 4 Sheets-Sheet 2 INVENTOR.

JOE H. LAMB ATTORNEYS J. H. LAMB Aug. 28, 1962 EXTENDIBLE AND RETRACTABLE COVER APPARATUS FOR SWIMMING POOLS 4 Sheets-Sheet 3 Filed Aug. 7, 1961 INVENT OR. JOE H. LAMB ATTORNEYS I I L I I I l l l I I l l l I I l a a r 9 J. H. LAMB Aug. 28, 1962 EXTENDIBLE AND RETRACTABLE COVER KPPARATUS FOR SWIMMING POOLS 4 Sheets-Sheet 4 Filed Aug. 7, 1961 JOE H. LAMB IN V EN TOR.

ATTORNEYS 3,950,743 EXTENDBLE AND RETRACTABLE COVER APPARATUS FOR MG P8015 Joe H. Lamb, Salt Lake City, Utah, assignor to Philip A. lf/iallinckrodt, Salt Lake City, Utah Filed Aug. 7, 1961, Ser. No. 129,831 12 Claims. Jl. 4-172) extension and retraction of a rolled cover sheet positioned at and extending along one end of the pool. The strips are provided with respective re-entrant slideway channels extending along their lengths for receiving and retaining thickened portions or beads provided along the longitudinal edges of the cover sheet as slides. Draw cords extend from the outer end of such cover sheet as longitudinal prolongations of the beads and double back over suitable guides at the far ends of the slideway strips to return to respective reels associated with the rolled cover sheet at the one end of the pool.

An outstanding object in the making of the invention was to provide apparatus of the type concerned wherein the sheet of flexible material is securely anchored to unobtrusive, laterally disposed, slideway structure during extension and retraction and while extended, and is easily and smoothly moved through its extension and retraction strokes.

Other important objects were to provide for controlled feed of the rolled sheet material to anchoring slideway channels of the slideway structure during extension and for controlled feed of the extended sheet material back to rolled condition during retraction, so operation will be smooth and free from bind and so that the sheet will be evenly and compactly rolled; to enable utilization of the same mechanism for both unwinding and rewinding the roll; to achieve rapid and trouble-free operation at minimum expense; and to provide an overall compact and unobtrusive construction especially adapted for use as a protective cover for swimming pools of all shapes and sizes.

Major features in the attainment of these objects, are the making of the elongate drum upon which the sheet is wound sufiiciently shorter than the width of the sheet to accommodate the beaded edges of the latter in overhanging relationship with the respective opposite ends of such drum and to thereby enable the sheet to be wound smoothly, evenly, and compactly on the drum and to be just as smoothly and evenly unwound therefrom; the mounting of the sheet-winding drum and of draw cord reels in common but for rotation independently, and the use of clutch means between shaft components, so that the reels and the drum may be driven alternately on what is essentially a single shaft; the provision of free-swinging pilot pieces at the bead-receiving and feeding ends of the respective carrier strips and on pivot axes normal to the drum axis, for both controlling bead entry into the anchoring slideway channels of such carrier strips and discharge thereof so the head will not build up on itself as the cover sheet is rolled on the drum; and the provision of independently adjustable brake means for the draw cord reels.

An outstanding feature necessary to efiective operation is the provision of sufficient slack in the cover to enable the portion thereof intermediate its margins to float on the water in the pool and to thus be supported, so there will be no undue binding of the beaded edges against the lips of the slideway strips which define the respective slideway channels thereof and consequent frictional resistance to extension and retraction.

Apparatus representing what are presently regarded as the best modes of carrying out the invention are illustrated in the accompanying drawings.

In the drawings:

FIG. 1 represents a top plan view of a typical rectangular, swimming pool equipped with a power operated, extendible and retractable, flexible sheet cover apparatus conforming to the invention, the cover being in its extended, pool-protective position and a representation of a kidney-shaped pool being indicated by broken lines to show how the same apparatus may be applied to differently shaped pools;

FIG. 2, a similar view of the same pool, with the flexible sheet cover retracted and the protective cover over the operating mechanism removed, the broken line representation of the kidney-shaped pool being eliminated from this view;

FIG. 3, -a transverse vertical section taken on the line 33 of FIG. 1 and drawn to'a considerably enlarged scale, the cover wind-up drum and draw cord reels being shown in elevation, with portions 0 fthe protective housing and intermediate portions of the drum being broken out for convenience of illustration;

FIG. 4, a similar view taken with respect to FIG. 2;

FIG. 5, a transverse vertical section taken on the line 5-5 of FIG. 2, showing the cover Wind-up drum and draw cord reels in longitudinal axial section;

FIG. 6, a longitudinal vertical section taken on the line 65 of FIG. 1, this view being drawn to the enlarged scale of FIGS. 3 and 4 and having an intermediate portion of the pool and cover apparatus broken out for convenience of illustration;

FIG. 7, a fragmentary section taken on the line 6-6 of FIG. 1 and drawn to a greatly enlarged scale;

FIG. 8, a similar section taken on the line 7-7 of FIG. 1;

FIG. 9, a fragmentary section taken on the line 8-8 of FIG. 1 and drawn to the scale of FIGS, 6 and 7;

FIG. 10, a wiring diagram.

FIG. 11, a view corresponding to that of FIG. 5 but illustrating a somewhat diflerent construction;

FIG. 12, a view corresponding to that of FIG. 6, but illustrating the construction ofFIG. 11;

FIG. 13, a fragmentary vertical vertical section taken on the line 13-43 of FIG. 11 and drawn to a larger scale;

FIG. 14, a similar view taken on the line 14-14 of FIG. 11; and

FIG. 15, a fragmentary horizontal section taken on the line 1515 of FlG. 13 and drawn to a still larger scale.

Referring to the drawings:

In the illustrated construction, the swimming pool 15 is of concrete and rectangular in form. However, it may be of any construction and of various configurations, as indicated by the dotted line representation in FIG. 1', without precluding effective application thereto of the apparatus of the invention.

The apparatus comprises slideway structure, which in.

the illustrated embodiment, takes the form of carrier strips 16 firmly secured to the flat and horizontal peripheral margins of the pool at the two longitudinal sides and one end thereof. They provide protective guides for the extension and retraction of a flexible and im- 1 by bearing stands 30 and 31 pervious cover sheet 17, which, in retracted condition, is rolled upon a drum 13 extending along the other end of the pool.

The carrier strips 16 advantageously comprise individual elongate shapes extruded from a corrosion-resistant material, such as aluminum, and aligned end to end by means of short pieces 19, FIG. 7, which are inserted in bottom grooves 29 to cross the respective lines of abutment between the individual shapes. Screws 21, driven into wooden pags 22 which are anchored in the concrete bordering the pool, represent one way of fastening the strips 16 in place along-opposite lateral sides of the pool. Another practical way is to use a water-insoluble adhesive, such as an epoxy resin, to adhere the strips directly to the surface of the concrete. However, the most preferred way is as disclosed in my copending application Serial No. 108,466, filed May 8, 1961, entitled Swimming Pool Cover and Method of Installing Same.

The slideway or carrier strips 16 are provided with longitudinally open, re-entrant, slideway channels 23 extending longitudinally thereof along both margins. Those slideway channels'23 facing the pool are utilizer for resaves ceiving, retaining, and guiding the longitudinal edges of the cover 17, which are enlarged by the provision of beads 17a for the purpose. Such beads fit into, are retained by, and slide along the interiors of the respective channels as anchor slides, while the cover sheet extends through and slides along the narrow longitudinal openings 24. Their contact with the defining margins of slit openings 24 effectively seals against the entrance of dust and dirt, wind, insects, etc.

The apparatus of the invention also includes means for pulling the outer end of the cover along the length of the pool, to extend the cover and thereby enclose the pool, and means for rotating the cover wind-up drum in an appropriate direction relative to the pool to retract such cover when desired.

Thus, draw cords 25, FIG; 6, extend from the outer end of cover 17 as longitudinal prolongations of the respective beads 17a, and are protectively received and guided by those slideway channels 23 that face outwardly from the pool. Such draw cords 25 are looped about pulleys 26, FIG. 9, which are mounted at the ends of carrier strips 16 remote from cover wind-up drum 13.

The free ends of these draw cords 25 are wound upon respective reels 27-1 and 27-2, FIG. 3, which are advantageously rotatably mounted in common with the cover wind-up drum 18 in an elongate pit 28, FIGS. 2 and 5, provided along one end of the pool 15.

For alternately rotating reels 27 and cover wind-up drum 18 in appropriate directions relative to the pool, so as to alternately extendand retract pool cover 17, the drum and reels are independently mounted on an elongate shaft 29, which, in turn, is rotatably mounted within a protective housing 32 sunk in pit 2.8.

Drum 18 is advantageously a hollow metal cylinder, cover sheet 17 being fastened thereto by large-headed nails 18-1, FIG. 5, driven through undersized receiving holes drilled through the metal. In order to insure smooth and even rolling and unrolling of cover sheet 17 .with its beaded edges 17a, drum 18 is made shorter than the width of such cover sheet, whereby the beaded margins loosely overhang the protruding portions of shaft 29, see FIG. 5. r

Drum 18 is mounted for free rotation on shaft 29, between bearing standards 39 and 31, by means. of a central supporting disk and hub 33 and opposite end disks. and'hubs 34 and 35', respectively, the hubs 34a wand 35a of the latter being elongate sleeves which extend through and are journaled in inner bearings 39a and 31a of the bearing stands.

Sleeve 34a terminates at its outer end in a clutch dog formation 34b, FIG. 3, adapted to be engaged by a mat- A 7 ing clutch dog formation 36a of a collar 36 when shaft 29 is pushed to the left, as in FIGS. 4 and 5, from the disengaged position of FIG. 3. Collar 36 is fixedly secured to shaft 29, as by means of set screws 37.

Shaft 29 is moved back and forth in the supporting hubs of drum 18 and in the outer bearings 3t3 b and 3% of bearing standards 30 and 31 by means of a cam and cam slot connection with the output shaft 38 of a speed reducer 39 associated with a reversible electric motor 40.

and when it is rotated counterclockwise, it pushes shaft 29 to the left while transmitting rotary movement thereto.

The draw cord reels 27-1 and 27-2 are freely rotatable on shaft 29 between the irmer and outer bearings of respective bearing stands 30 and 31. Reel 27-1 has the inner end of its hub formed as a clutch dog 45 adapted to mate with a clutch dog 36b formed at the opposing end of collar 36. Reel 27-2 has the outer end of its hub formed as a clutch dog 46 adapted to mate witha clutch dog 47a formed at the opposing end of a collar 47 which is secured to the free end of shaft 29 as by means of set screws.

Clutch dogs 45 and 36b of reel 27-1 and clutch dogs 46 and 47a of reel 27-2 are arranged to transmit clockwise rotation to the respective reels when thrown into interengagement by reason of the pulling of shaft 29 to the right when it is rotated clockwise by clockwise rotation of drive shaft 38 transmitted by cam coupling 41, see FIG. 3. In the illustrated instance, considering the overhand winding of draw cords 25 on reels 27-1 and 27-2, see FIG. 6, clockwise rotation of such reels effects winding of the draw cords thereon and concomitant pulling on the leading end of cover sheet 17 to unwind such cover sheet from its rolled position on wind-up drum 18, see FIGS. 2, 4, and 5, and to pull it over and along the length of pool 15 to the extended, pool enclosing position of FIGS. 1, 3, and 6. Since clutch dogs 34b and 36a are disengaged during this time, such drum will rotate freely on shaft 29, paying out cover sheet 17 as required.

Counterclockwise rotation of drive shaft 38 will, on

p the draw cord reels and wind-up drum serves very advantageously for push-button, power operation. Thus,

a manually operated electrical switch 48, FIG. 10, having forward, reverse, and off positions, is interposed in'the powersupply circuit of motor 40,.in this illustrated embodirnent of the invention, as is, also, a conventional circuit breaker 4-9 of overload type. V

17 into pool-enclosing position and to Reverse to retract such cover sheet. Stopping of each operation at its termination is automatic when excessive current tends to be drawn by the motor. Stopping is similarly automatic in the event the slideway channels 23 or anchor slides 17a become damaged and binding occurs."

A motor of one-quarter horsepower geared :down to sixty rpm. at the output'shaft has beerrfoundvery satisfactory for most installations.

In guiding draw cords 25 onto reels 27, swivel-mounted It is only necessary" to move switch 48 to Forward? to extend cover sheet pulleys 50, FIG. 6 are advantageously utilized within housing 32. A housing cover 51, substantially flush with the margins of the pool, serves to hide and protect all the aforedescribed operating mechanism. Both cover sheet 17 and draw cords 25 pass through a narrow slot 52 between the forward margin of cover 51 and the adjacent pool margin.

As a feature of the invention, resiliently activated, independently adjustable brakes 53, FIGS. 3-5, are mounted in bearing stands 39 and 31, respectively, to frictionally bear against the reels 27-1 and 27-2, respectively, and prevent inadvertent unwinding or override due to momentum. Their independent adjustability is very important in connection with even operation of the system, since this makes it possible to compensate for any struc tural irregularities which would otherwise cause the cover sheet to be extended or retracted unevenly. Adjustability is had in any suitable manner, e.g. as shown in connection with the embodiment of FIGS. 12-15.

A significant feature of the invention is the provision of free-swinging pilot pieces 54, FIGS. 1,2, and 8, immediately in advance of the respective inner slideway channels 23 for controlling both feed of the beads 17a into such channels and guided discharge from such channels and onto drum 18. There are two of these members 54, each advantageously made of a rigid and durable plastic material, such as nylon, to simulate a slideway channel portion of a short length of the carrier strip 16 and each pivotally secured as a prolongation of the fixed slideway structure, as by means of a screw-in pivot pin 55,. Irregularities of position and alignment of the beads 17a relative to the slideway channels 23 are ironed out, so to speak, by the free swinging action of pilot members 54, through the sl-ideway channels 56 of which such beads 17a are threaded. Wedging and binding of such beads during extension of the cover sheet are precluded by this arrangement, as is winding or rolling of such beads on themselves during retraction of such cover sheet. As illustrated, it is preferred that a section of each strip 16 be cut out to accommodate the pilot piece and its swinging action.

As previously indicated, there must be enough slack in the cover sheet 17 to allow it to float on the surface of the water intermediate its margins and to allow for contraction due to temperature change.

In order to complete the peripheral sealing of cover sheet 17 against entry of wind and foreign matter, it is preferred to utilize a seal strip 57 along the end of the pool 15 for sealing cooperation with the leading edge of such cover sheet. For the sake of symmetry, it is preferred that the seal strip 57 be identical with the slideway strips 16 and that the leading edge of cover sheet 17 be prepared for sealing cooperation with the inner channel 58 thereof by the application to such leading edge of a rigid supporting strip 59, FIGS. 1, 2, and 6, which forms the subject of my 'copending application Serial No. 131,- 049, filed August 7, 1961, entitled Carrier for Forward Edge of Extendible and Retractable Flexible Sheet.

Such strip 59 is conveniently an extruded length of some non-corrosive material, such as aluminum, formed with an open-ended, cylindrical portion 59a extending along its length, where non-rectangular pools are involved, shafts 60 protrude at both ends of such portion to receive respective wheeled supporting carriages 61 with offset axles, which travel on the pool margins alongside the respective slideway strips 16 and serve to elevate and support strip 59 during extension and retraction, all in accor-dance with said .copending application Serial No. 131,049. A forwardly protruding lip portion 59b of such supporting strip 59 is guided into channel 58 at the tennination of each cover-sheet-extending operation, where it fits directly into channel 58 or into a sealing strip 62 of rubber or the like inserted in such channel 58.

For securing supporting strip 59 to cover sheet 17, the

6 leading edgeof the latter is formed with a bead 17b, FIG. 6, which is snugly received and secured by and along the re-entrant channel of a slideway member 59c formed integral with and projecting backwardly from and along the rear margin of supporting strip 59.

Housing 32 may be constructed with the unique features (not shown) presented in detail in my copending application Serial No. 126,130, filed July 24, 1961, entitled Protectively Housed Extendible and-Retractable Cover Apparatus for Swimming Poo-ls.

The motor-reversing switch 48 schematically illustrated in FIG. 10 is a commercially available, multiple-path, drum switch, such as that manufactured by Furnas Electric Co., Batavia, 111., and offered as its style R44R, although most any reversing switch may be employed for the purpose.

The apparatus of the invention is well adapted for providing a weather-excluding shelter over the pool area, while still permitting use of the pool for swimming. For this purpose, a suitable sealant (not shown) is interposed between the concrete pool surface and the bottom surfaces of both the carrier strips 16 and end seal strip 57 and additional slack is provided in the cover sheet. By injecting air beneaththe extended cover sheet in any suitable manner, it is billowed upwardly, leaving surlicient space therebelow to accommodate swimmers.

There are many different ways of constructing a swimming pool. The illustrated form of the invention is concerned with a pool constructed in one of the more common ways. While differences in pool construction may require certain changes in the apparatus of the invention, many such changes will involve only obvious structural details. For example, in some instances it may be desirable to place the strips 16 on the vertical faces of the pool walls, rather than on the horizontal margins- This would enable either set of slideway channels of the carrier strip to be utilized as slideway anchorage for the cover beads. Similarly, the operating mechanism need not be underground, as in the pit 28, but can rest on the surface; Even so, the general structural and functional features of the apparatus will remain the same.

The embodiment of FIGS. 11-15 incorporates many details of construction which are presently preferred. Thus, the two reels 70 for the respective draw cords 71 are mounted for rotation in respective supporting frames 72, each made up of a U-shaped, reel-supporting, lower section 72-1 and an inverted U-shaped, hood-like, upper section 72-2, the two sections having flanges 72-1a and 72-2a, respectively, which are joined in face to face rela tionship, as by welding, see FIG. 13. The lower'fiange's 72-1a continue beyond the upper ones, and, together with companion flanges 72-1b, serve to support lower pillow blocks 73, which, with upper pillow blocks 74, journal stub shaft portions-70a of reels 70.

-The upper section 72-2 of each frame 72 serves to mount, along its rearward margin, an elongate block 75 equipped with spaced pulleys 76 and 77 for leading the particular draw cord 71 concerned from reel to cover sheet and vice versa during extension and retraction of such cover sheet. That section of the block which mounts pulley 76 above the particular reel 70 concerned is canted downwardly as shown in FIGS. 11 and 1 4 to better guide the draw cord from and back on the reel.

To better retain the draw cords on the respective reels 70 during all phases of extension and retraction of the cover sheet, rollers77 are mounted on respective shafts 78 which are fastened in and extend across the widths of respective frames 72 at spaced locations about the lower circumferences of such reels 70.

The clutch drive mechanism for both drum and reels is essentially the same as in the first embodiment. Thus, the wind-up drum 79 on which the cover sheet is rolled is secured to a tubular shaft 80 which terminates at one of its ends in a'clutch dog formation 80a, FIG. 11, adapted sleeve 81 being provided with a dog 83, rigid therewith,

for engagement by a clutch dog formation 81b atthe'opposite end of such sleeve 81. A clutch dog 84 is secured at one end of shaft 82 for engagement with an adjacent clutch dog formation 85 rigid with the other reel 71. As in the first embodiment, a cam coupling 41 connects the opposite end of shaft 82 with the output shaft 38 of a speed reducer 39 driven by a reversible electric motor 49 and shifts such shaft 82 back and forth to engage one or the other of the respective sets of clutch dogs for either extending cover sheet 86 relative to housing 87 and the swimming pool 88 or retracting it relative thereto.

' In the present instance cover sheet 86 is given sufiicient slack to drop precipitously down the walls of the pool, see

FIG. 12, so that practically all of it floats on top of the water 89 in such pool. In this connection it is advisable to cover the pool ledge 88a, over which the cover sheet rides in its extension and retraction movements, with smooth tile 90 to prevent abrasion and facilitate smooth operation.

As previously mentioned, a very important feature of the invention is the provision of independently adjustable brakes for the respective draw cord reels 70. As shown in FIG. 15, a set of two friction brakes 91 is provided for each reel, the individual brakes being preferably disposed in diametrical opposition at one face of the reel. Each brake comprises a brake shoe 92 resiliently urged toward such face of the reel by means of a coil spring 93, which is adjustably tensioned by a cap screw 94 threaded in the outer 'end of a tube 95 housing both the shoe and the spring.

These independently adjustable brakes on the reels 70 play a very important part in insuring evenness of retraction of the cover sheet. There is a great tendency for the cover sheet to roll unevenly due to the thickened longi' tudinal edges. If the overall diameter of the roll, including the margins, is not substantially uniform, troubles arise.- Thus, differences in the compactness of the two ends of the roll between themselves will cause the cover sheet to cant'one way or the other and cause binding of the edge beading in the slideway channels. Even if these ends are of the same diameter, if they are larger in diameter than the diameter of the intermediate portion of the roll, there is slack intermediate such ends within the housing which will loop down between the roll and forward wall of the housing during extension of the cover sheet and catch, putting undue strain on the motor and throwing the circuit breaker in the electrical supply system.

These difficulties are overcome by so adjusting the brakes that the beads roll up tightly and evenly during retraction of the cover sheet, much as illustrated in'FIG.

. 5. The greater the frictional drag on the reels, the tighter the rolling of the edgebeads. Due to inevitable irregularities in structure, and to shrinkage, and thermal expansion and contraction, it has been found necessary to make the frictional drag adjustable with respect to both reels and, desirably, with respect to diametrically opposite out and distinctly claimed herebelow.

I claim; 7 V

1. Rolled sheet extendingjand retracting apparatus, comprising an elongate drum; shaft means mounting the drum for rotation and extending from opposite ends of said drum; a sheet of flexible material having width greater than the length of the drum and wound thereon with the longitudinal edges of said. sheet overhanging the ends thereof; guideway means spaced from .said drum and having re-entrant slideway channelsdisposed laterally of and extending along the area of extension and retraction of said sheet at respectively opposite sides of said sheet, said sheet having its opposite longitudinal edges continuously beaded and received by said slideway channels as anchor slides adapted for sliding movement therealong in the extension and retraction of the sheet; draw cords attached to the outer end of the sheet as prolongations of the respective beaded edges of such sheet; return guideway means substantially paralleling the first-named nels of said guideway means, the beaded edges of said sheet being received by said channels of the guide pieces for sliding movement therethrough in passing from and back to said drum;,-reels mounted on said shaft means at opposite ends of the drum, respectively, and beyond the zones of overhang of said margins of the sheet, said draw cords passing back through said return guideway means, respectively, and being secured to said reels, re-

spectively, for winding thereon as the sheet is extended;

and means for alternately driving the reels and the drum for alternately extending and retracting said sheet.

.2. The apparatus of claim 1, additionally including independently adjustable brake means in operative association with the respective reels, for exerting drag thereon during extension of the sheet.

3. The apparatus of claim 2, wherein the brake means comprise respective sets of independently adjustable brakes, the brakes of each set being disposed at diametrically opposite locations with respect to their particular reel. a

4. The apparatus of claim 1, wherein the means for alternately driving the draw cord reels and the wind-up drum comprise a motor; the shaft means comprise an elongate shaft, on which said reels and said drum are independently mounted for free rotation, the motor being coupled in drive relationship with the shaft; means for reversing the direction of rotation of said' shaft; and clutch means for alternately effecting rotation of said reels and said drum in opposite directions during rotation of said shaft.

5. The apparatus of claim 4, wherein the motor is a 3 reversible electric motor and is coupled to the shaft by a cam coupling which serves to push or pull the shaft longitudinally depending upon the direction of rotation of the motor; and wherein the clutch means include'interengaging members fixed to said shaft and to said reels and drum, respectively, for interengage'ment and for separation, depending upon the direction of rotation of the motor and the direction of longitudinal movement .of said shaft.

6. Rolled sheet extending and retracting mechanism comprising an elongate shaft; bearing means mounting said shaft for rotation and for back and forth longitudinal movement; an elongate drum rotatably mounted on said shaft. and adapted to carry a sheet of material rolled thereon; a pair of reels rotatably mounted on theshaft at opposite ends of said drum, respectively, and adapted to wind thereon respective draw cords extending from said sheet; means confining the drum .and said reels against axial movement longitudinally of the shaft; means for rotating the shaft in either one direction or the other and for pushing or pulling the shaft axially longitudinally;

clutch members on the shaft and on the drum, respectlvely, for interengagement when the shaft is at one of its extreme longitudinal positions; and clutch members on the shaft and on the reels, respectively, for interengagement when the shaft is at the other of its extreme longitudinal positions.

7. In a rolled sheet extending and retracting apparatus which comprises a sheet of-impervious flexible material; means for storing said sheet and for extension and retraction of the sheet therefrom; slideway. structures spaced from said means and secured along respective opposite, lateral, sides of the path of sheet extension and retraction and having respective, longitudinally open, slideway channels extending longitudinally of said path for receiving,

spaced from said drums and pivotally mounted at the adretaining, and guiding opposite longitudinal edges of said sheet, respectively, the longitudinal opening of each ,channel being narrow relative tothe interior thereof and said edges of the sheet being enlarged continuously as beading for retention within the respective channels to serve as anchor slides, the sheet itself extending through and being slidable along said longitudinal openings of the channels; means for pulling the outer end of said sheet along the length of said path for extending said sheet through the area of said path; and means for retracting said sheet; guide pieces spaced from said retracting means and pivotally mounted at the rearward ends of the respective slideway structures on axes askew of said retracting means,

said guide pieces having respective re-entrant channels disposed as continuations of said slideway channels of the slideway structures, the beaded edges of said sheet being received by said channels of the guide pieces for sliding movement therethrough during extension and retraction of said sheet.

8. In combination with a swimming pool, an extendible and retractable cover apparatus therefor, comprising an elongate drum; shaft means mounting the drum for rotation along one end of the pool and extending from opposite ends of said drum; a sheet of flexible material having width greater than the length of the drum and wound thereon with the longitudinal edges of said sheet overhanging the ends of said drum, said sheet having width and length adapted to completely cover the pool and suflicient slack to drop to the normal level of water in the pool; guideway means spaced from said drum and having re-entrant slideway channels disposed laterally of and extending along the area of extension and retraction of said sheet at respectively opposite sides of said sheet, said 'sheet having its opposite longitudinal edges continuously headed and received by said slideway channels as anchor slides adapted for sliding movement therealong in the extension and retraction of the sheet; draw cords attached to the outer end of the sheet as prolongations of the respective beaded edges of such sheet; return guideway means substantially paralleling the first-named guideway means; guide means at the outer ends of said guideway means and of said return guideway means, about which the dIZilW cords are looped, respectively, in passing from one to the other of said guideway means; guide pieces jacent ends of the respective guideway means on substantially vertical axes, said guide pieces having respective re-entrant channels disposed as continuations of said mutually opposing slideway channels of said guideway means, the beaded edges of said sheet being received by said channels of the guide pieces for sliding movement therethrough in passing from and back to said drum; reels mounted on said shaft means at opposite ends of the drum, respectively, and beyond the zones of overhang of said margins of the sheet, said draw cords passing back through said return guideway means, respectively, and being secured to said reels, respectively, for winding thereon as the sheet is extended; and means for alternately driving the reels and the drum for alternately extending and retracting said sheet.

9. The combination set forth in claim 8, wherein the reels are mounted in and the shaft is supported by respective frames, each comprising a U-shaped, reel-supporting, lower section and an inverted U-shaped, hoodlike, upper section; and wherein the draw cords are guided to and from the reels by spaced pulleys of elongate blocks secured across the tops of respective 10. The combination set forth in claim 9, wherein there are additionally provided sets of independently ad- 1 justable brakes for the respective reels, each of said sets including resiliently actuated brake shoes in the form of pairs of spring-biased pins, the individual pins being mounted in the respective frames diametrically opposite each other relative to the reel.

11. The combination set forth in claim 1, wherein the reels are mounted in and the shaft is supported by respective frames, each comprising a U-shaped, reel-supporting,

lower section and an inverted U-shaped, hood-like, upper section; and wherein the draw cords are guided to and from the reels by spaced pulleys of elongate blocks secured across the tops of respective trames.

12. The combination set forth in claim 11, wherein there are additionally provided sets of independently adjustable brakes for the respective reels, each of said sets including resiliently actuated brake shoes in the form of pairs of spring-biased pins, the individual pins being mounted in the respective frames diametrically opposite each other relative to the reel.

References Cited in the file of this patent UNITED STATES PATENTS 1,114,716 Annable Oct. 27, 1914 1,578,641 Bywater Mar. 30, 1926 1,800,654 Nelson Apr. 14, 1931 2,754,899 Karobonik et a1. July 17, 1956 FOREIGN PATENTS 14,672 Great Britain July 10, 1908 786,061 France June 3, 1935 

